/* 公共的样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
    background-repeat: no-repeat;
    background-position: center;
    background-size: cover;
}

.nav {
    width: 100%;
    height: 50px;
    background-color: rgb(51, 51, 51);
    color: white;
    display: flex;
    align-items: center;
    padding-left: 20px;
}